In recent years, it has strongly been desired in the field of portable electronic instruments such as portable telephone, and pager to prolong display time without exchange of battery in addition to reduction of size and weight. It is thus severely required that a display device build in a portable electronic instrument less consumes the power.
The inventor had widely studied liquid crystal display devices which are of one of various display types, in view of reduction of power consumption.
As a result, it has been found that the conventional liquid crystal display devices had their power supply circuit for supplying a power voltage, which itself consumed very large amount of power. The power supply circuit required about 1/3 of the power to be consumed in the liquid crystal display device.
To overcome such a problem as described, an object of the present invention is to reduce the power consumption of the power supply circuit itself and thus the power consumption in display devices and electronic instruments that use such a power supply circuit.